In the past, in order to make it possible to reuse paper printed for the purpose of temporary transmission, display, and the like of information, for example, a heat sensitive recording medium (thermal recording paper), printing on which is erased by heat, and a pigment, color of which is erased by heating, are used.
Further, as a toner of an image forming apparatus such as a MFP (Multi Function Peripheral), a so-called decolorable toner, a color of which is erased by heating, is also used. Since a sheet on which an image is formed with the decolorable toner is decolored by heating, the sheet can be reused after being decolored.
However, the decolorable toner in the past has insufficient decoloring performance. For example, a gloss in a decolored portion of an image formed on a sheet is conspicuous.